The factors leading to alcohol abuse and alcoholism remain unclear. For years, stress has been thought to influence the effects of ethanol. Recently, brain levels of some CNS-active steroids have been reported to increase during stress. In addition, these 'neuroactive' steroids modulate ionotropic receptor systems in common with those influenced by ethanol. Such findings suggest an important, yet relatively unexplored, relationship among the effects of stress, ethanol and neuroactive steroids. Proposed experiments will employ the drug discrimination procedure to address the specific aims, which are: 1) To assess the role of neuroactive steroids in discriminations of qualitatively different doses of ethanol under non-stressful and acutely stressful conditions in rats, and 2) To assess the effects of differential exposure to stressful conditions or neuroactive steroid administration on the discriminative stimulus effects of a low dose of ethanol in rats. As the discriminative stimulus effects of a drug may include those effects involved in the maintenance of drug-taking behavior, results may suggest differential vulnerability to the addictive properties of alcohol as a function of the pattern of stress and/or the endogenous levels of neurosteroids to which an individual is exposed. These findings will broaden our current understanding of the roles of stress exposure and neuroactive steroids in the development of alcohol abuse and alcoholism.